1. Field of Invention
The present invention relates to a fuel cell, and more particularly to an electrochemical fuel cell comprising a particulates blocking device which effectively filters and prevents ultra-fine organic particulates from entering into fuel cell, so as to significantly prolong a life span thereof.
2. Description of Related Arts
Referring to FIG. 1 of the drawings, a conventional fuel cell typically comprises a membrane electrode assembly 1, a fuel storage reservoir 2 adapted for storing fuel hydrogen of the fuel cell, a pressure-relief valve 3 connected with the fuel storage reservoir 2 for adjustably releasing hydrogen fuel, an air filter 4 adapted for filtering incoming air, an air compressor 5 connected with the air filter 4 for compressing the in coming air into a predetermined pressure, a water-vapor separator 6, a water tank 7, a water pump 8, a heat exchanger 9, and a hydrogen circulating pump 10.
As a matter of conventional art, the fuel cell is a particular kind of electrochemical energy conversion device which is capable of converting the hydrogen and oxidant into electrical energy. The core part of the fuel cell is the membrane electrode assembly 1 (MEA). The MEA 1 usually comprises a proton exchange membrane sandwiched by two porous sheets made of conductive material such as carbon tissue. At the same time, a layer of catalyst like metal platinum powder, adapted for facilitating the electrochemical reaction, are evenly and granularly provided on two layers of carbon tissue to form two catalytic interfaces. Furthermore, electrically conductible members are provided on two sides of MEA to form a cathode and an anode, in such a manner, electron generated from the electrochemical reaction are capable of being lead out through an electrical circuit.
The anode of the MEA is supplied with fuel, such as hydrogen, for initiating the electrochemical reaction. The fuel is forced through the porous and diffused carbon tissue, and is capable of being deionized on the catalytic interface for the loss of electrons to generate positive ions. Moreover, positive ions are capable of transferably penetrating the proton exchange membrane to reach the cathode. On the other hand, an oxidant-containing gas, such as air, is supplied to the cathode of the MEA. Accordingly, the oxidant-containing gas is able to penetrate the porous and diffused carbon tissue to be ionized for the addition of the electrons to generate negative ions. Finally, the positive ions transferred from the anode will meet the negative ions to form reaction product.
In the electrochemical fuel cells which employ the hydrogen as the fuel and oxygen containing air as the oxidant, the electrochemical reaction on the anode generates hydrogen positive ions (protons). The proton exchange membrane is capable of facilitating the hydrogen positive ions migrate from the anode to the cathode. In addition, the proton exchange member has another function as a separator for blocking hydrogen containing air flow from being directly contacted with the oxygen containing air flow so as to prevent the mixture of hydrogen and oxygen as well as the explosive reaction.
The electrochemical reaction on the cathode side of fuel cell generates negative ions by obtaining the electrons. As a result, the negative ions generated on the cathode side will attract the positive ions transferred from the anode side to form water molecule as reaction product. In the electrochemical fuel cells which utilized the hydrogen as the fuel and oxygen containing air as oxidant, the electrochemical reaction is expressed by the following formula:Anode: H2→2H++2e Cathode: ½O2+2H++2e→H2O
In the typical proton exchanging membrane fuel cell, the MEA is disposed between two electrically conductible electrode plates wherein the contacting interface of each electrode plate at least defines one flowing channel. The flowing channel could be embodied by conventional mechanical method such as pressure casting, punching, and mechanical milling. The electrode plate could be embodied as metal electrode plate or graphite electrode plate. So the flowing channels defined on the electrode plate are capable of directing fuel and oxidant into anode side and cathode side respectively positioned on opposite side of the MEA. For a single fuel cell structure, only one MEA is provided and disposed between an anode plate and a cathode plate. Here, the anode plate and the cathode plate not only are embodied as current-collecting device, but also as a supporting device for securely holding the MEA. The flowing channels defined on the electrode plate are capable of delivering fuel and oxidant to the catalytic interfaces of the anode and cathode, and removing the water discharged from the electrochemical reaction of fuel cell.
To increase the overall power output of the proton exchanging membrane fuel cell, two or more fuel cells are electrically connected in series with a stacked manner or a successive manner to form a fuel cell stack. In such stacked series manner, each electrode plate comprises flowing channels defined on opposite side of plate respectively wherein one side of the electrode plate is applied as an anode plate contacting with the anode interface of a MEA, while another side of the electrode plate is applied as a cathode plate contacting with the cathode interface of an adjacent MEA. That is to say, one side of such electrode plate serve as an anode plate for one cell body and the other side of plate serve as a cathode plate for the adjacent cell. Within the art, this kind of structure is called bipolar plate. However, in the successive series manner, a plurality of single cell bodies are connected successively, wherein a front end unipolar plate and rear end unipolar plate as well as a fastening member are provided to form an overall fuel cell.
It has been practiced in the art to use such fuel cells as power unit for propelling vehicles including four-wheeled motor vehicles and motorcycles and operating other electrically operated machines such as portable generators.
A primary object of the fuel cell power unit for propelling vehicles, ships, and portable generators is to provide an extended and stable service. As a result, to guarantee the stable service, the fuel gas supplied to the fuel cell like hydrogen and oxidants containing air are required to be of a good quality. Nowadays, a common method for supplying quality air and hydrogen to the fuel cell is to equip the fuel cell with an air filter and a hydrogen filter for screening the dust of micron and submicron sizes in the air.
However, there exist adverse factors which affect (shorten) the lifespan of the conventional fuel cell, the main being the existence of dust of micron and submicron sizes, plus the general failure to block those extra small particulates entering into the fuel cell. Moreover, there also exist by a kind of organic oily molecules, which are of ultra-submicron size, suspended and mixed with normal air molecules. This kind of organic oily molecules is capable of penetrating through the most precise filter and enters into the fuel cell. The overall performance of the fuel cell is definitely affected, and the culmination of those ultra small particulates inside the fuel cell would eventually deteriorate the original chemical and physical interaction of all the elements of the fuel cell, thus significantly reducing the lifespan of the conventional fuel cell in question.